1. Field of the Invention
The invention relates generally to an electro-optical circuit board (EOCB). More particularly, the invention relates to an electro-optical circuit board (EOCB) having an optical transmit/receive module and an optical waveguide integrated, in which the optical transmit/receive module where the optical waveguide for transmitting an optical signal, a driving unit/receiving unit for converting an electrical signal into the optical signal, and vice versa, and an optical source/optical detector are integrated is manufactured, and the integrated optical transmit/receive module is attached within a trench formed in a printed circuit board, thus minimizing an alignment error between the optical source/optical detector and the optical waveguide and facilitating its manufacture.
2. Description of the Prior Art
As a technology of an integrated circuit (IC) is progressively advanced and the operating speed and the level of integration are thus improved, a higher performance of a microprocessor and a larger capacity of a memory chip are rapidly progressed. Accordingly, a next-generation information communication system having a large capacity parallel computer, an asynchronous transfer mode (ATM) switching system of over a terabit (Tb/s) level capable of transmitting information of a large capacity, or the like, requires a further improved signal processing capability. Due to this, there is a need for higher speed of a signal transfer and a higher density of a line.
In a conventional device, however, as information is usually transferred by means of an electrical signal between a relatively short distance such as between the board and the board or between the chip and the chip, there is a limitation in accomplishing a higher speed of the signal transfer and a higher density of the line. In addition, there is a significant problem that the signal is delayed due to the resistance of the line itself. Further, as the higher speed of the signal transfer and the higher density of the line may generate a noise due to electromagnetic interference (EMI), there is a need for a solution to solve these problems.
Recently, an optical line has been spotlighted as a solution for solving these problems. The optical line can be applied to various sections such as between the device and the device, the board and the board, or the chip and the chip. In particular, it is considered that the optical line is suited for an optical transfer communication system for the signal transfer in a relatively short distance such as between the chip and the chip.
Most of the patents relating to the conventional electro-optical circuit board (EOCB) include a silicon chip for transmittance based on a silicon substrate, an optical emitting unit, an optical board unit, an optical detector, a silicon chip for reception, or the like. Also, they include a lens for an optical coupling. This construction, however, is a modified type of the conventional optical transmit/receive module. It is thus consider that this type of the electro-optical circuit board (EOCB) is difficult to be used as the EOCB of a real sense that can be applied to the common PCB in order to solve the electrical interconnection problem.
A typical type of the conventional EOCB includes U.S. Pat. No. 6,324,328 entitled “Circuit Carrier with Integrated, Active, Optical Functions”. This patent uses an optical waveguide stacked within the PCB, as the optical line for transmitting the signal. However, this patent does not clearly disclose a solution for solving a problem relating to an alignment of the optical waveguide. It is thus considered that this patent is difficult to be implemented.
Another example includes a prototype utilizing an existing SMT system manufactured by NTT, Inc. (Japan). The prototype has a structure in which the VCSEL and a photo diode are sealed into a hole at the rear of a plastic BGA package and two polymer micro lenses are positioned on a single optical trace in order to magnify a mounting tolerance error. Further, this patent discloses that optical signals are transmitted in parallel between the IC packages and a mounting cost is significantly reduced.
However, this technology is difficult to be used due to three alignment errors: an error occurring when the optical waveguide is stacked within the PCB, an error occurring when the VCSEL is attached to the rear of the plastic BGA, and an error occurring due to a secondary interconnection when the plastic BGA is soldered to the PCB. Further, as this prototype has a structure in which the VCSEL is completed closed, there is a disadvantage that a heat generated from the chip is not dispersed or cooled.